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From: Fam Zheng <famz@redhat.com>
To: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Cc: linux-kernel@vger.kernel.org, famz@redhat.com
Subject: Re: [PATCH v4 4/9] epoll: Add implementation for epoll_ctl_batch
Date: Wed, 11 Mar 2015 10:23:10 +0800	[thread overview]
Message-ID: <20150311022310.GB1437@ad.nay.redhat.com> (raw)
In-Reply-To: <54FEF8C7.7050906@gmail.com>

On Tue, 03/10 09:59, Dan Rosenberg wrote:
> On 03/09/2015 09:49 PM, Fam Zheng wrote:
> > +	if (!cmds || ncmds <= 0 || ncmds > EP_MAX_BATCH)
> > +		return -EINVAL;
> > +	cmd_size = sizeof(struct epoll_ctl_cmd) * ncmds;
> > +	/* TODO: optimize for small arguments like select/poll with a stack
> > +	 * allocated buffer */
> > +
> > +	kcmds = kmalloc(cmd_size, GFP_KERNEL);
> > +	if (!kcmds)
> > +		return -ENOMEM;
> You probably want to define EP_MAX_BATCH as some sane value much less
> than INT_MAX/(sizeof(struct epoll_ctl_cmd)). While this avoids the
> integer overflow from before, any user can cause the kernel to kmalloc
> up to INT_MAX bytes. Probably not a huge deal because it's freed at the
> end of the syscall, but generally not a great idea.
> 

Yeah, makes sense, any suggested value?

Thanks,
Fam

  reply	other threads:[~2015-03-11  2:23 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-10  1:49 [PATCH v4 0/9] epoll: Introduce new syscalls, epoll_ctl_batch and epoll_pwait1 Fam Zheng
2015-03-10  1:49 ` [PATCH v4 1/9] epoll: Extract epoll_wait_do and epoll_pwait_do Fam Zheng
2015-03-10  1:49 ` [PATCH v4 2/9] epoll: Specify clockid explicitly Fam Zheng
2015-03-10  1:49 ` [PATCH v4 3/9] epoll: Extract ep_ctl_do Fam Zheng
2015-03-10  1:49 ` [PATCH v4 4/9] epoll: Add implementation for epoll_ctl_batch Fam Zheng
2015-03-10 13:59   ` Dan Rosenberg
2015-03-11  2:23     ` Fam Zheng [this message]
2015-03-10  1:49 ` [PATCH v4 5/9] x86: Hook up epoll_ctl_batch syscall Fam Zheng
2015-03-10  1:49 ` [PATCH v4 6/9] epoll: Add implementation for epoll_pwait1 Fam Zheng
2015-03-10  1:49 ` [PATCH v4 7/9] x86: Hook up epoll_pwait1 syscall Fam Zheng
2015-03-10  1:49 ` [PATCH v4 8/9] epoll: Add compat version implementation of epoll_pwait1 Fam Zheng
2015-03-10  1:49 ` [PATCH v4 9/9] x86: Hook up 32 bit compat epoll_pwait1 syscall Fam Zheng
2015-03-12 15:02 ` [PATCH v4 0/9] epoll: Introduce new syscalls, epoll_ctl_batch and epoll_pwait1 Jason Baron
2015-03-13 11:31   ` Fam Zheng
2015-03-13 14:46     ` Jason Baron
2015-03-13 14:56       ` Paolo Bonzini

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